How are you calculating frontal area? Did you go from a head on shot of Fabian in the TT position?
I am using A~0.36 - 0.38 m2 I change it depending on the rider. I just realized I input the air density wrong in my program. It should be 1.136 kg/m3 for Mendrisio @ 342 m elevation and 77°F. With that density I get around 493 W for Cancellara with no wind. Somewhere around 6.2 W/kg.
To be honest it is very difficult to do calculation for the time trial since the drag factor and frontal area are crucial for the calculations. I really don't have a good handle on these two values for time trials. I am going to read some information on this to educate myself a little more. So far I am depending on some matches that I have done on some power tabs from other cyclist in time trials and I try to depart from there. But that is it.
This what I have for frontal area for an average person (I don't have the height and weight details because I don't have the book with me now):
Vertical Commuter: 0.51 m2 (Cd=1.1)
Climbing: 0.44 m2 (Cd=0.99)
Racing: 0.36 - 0.38 m2 (Cd=0.88)
Drafting: 0.36 - 0.38 m2 (Cd= 0.5)
Moser: 0.42 m2 (Cd=0.51)
TT: Depends on the rider. I decrease or increase depending on Power Tab.
This is from the "Fluid Mechanics" book from McGraw-Hill. Here, anybody can do it:
Drag Power = (0.5)*(1.13689kg/m3)*((14.33 m/s)^2)*(0.69)*(0.38 m2)*(14.33 m/s) = 439 watts
The rest is rolling resistance, bearings and some kinetic losses. You get 493 Watts.
Add some wind and more weight and you have a formula for "disaster".